This invention relates to devices and methods for exerting a posteriorly-directed or distalizing force to a patient's upper posterior tooth, and an anteriorly-directed or protraction force to the lower jaw and teeth. The invention is particularly directed to orthodontic devices and methods which include a tooth attachment fixed to a patient's lower posterior tooth, and also include a bite bumper for transmitting the natural lower jaw pressure to an upper posterior tooth.
Many patients suffer from a bite condition in which the upper anterior teeth exhibit excessive horizontal overbite, termed “overjet”, and the lower molars bite too far back relative to the upper molars. This bite imbalance is called a “Class II malocclusion”. The imbalance can result from the lower (mandibular) jaw being too short, or the upper (maxillary) jaw being too far forward. Several devices, called “functional appliances”, have been used by orthodontists to hold the lower jaw forward from its retruded, uncorrected condition, and after a period of time wearing such a functional appliance, the bite becomes stable in the advanced, corrected position. This correction is due to shifting of the teeth within the jaws, and to differential growth caused by the appliance. To achieve this correction, the upper teeth are shifted posteriorly and the lower teeth and jaw are shifted anteriorly, reducing the overjet.
Overjet can also be treated by fixed intraoral distalizing devices which work exclusively on teeth in the upper jaw, using the roof of the mouth and the anterior teeth as an anchor to push posteriorly on the molar teeth. The upper teeth are moved posteriorly, or “distalized”, in two stages. In Stage I the upper molars are distalized with a fixed intraoral device or with standard orthodontic braces. Then in Stage II the remaining upper anterior teeth are distalized, frequently using elastic bands pulling back from the lower teeth and braces. During Stage II, forward relapse of molar correction is common. To minimize this relapse, a Nance button appliance is often attached to the molars as an anchor, holding them posteriorly while the anterior teeth are being retracted. Examples of fixed intraoral distalizing devices include the Jones Jig, the Hilgers pendulum, and the distal jet appliances. Disadvantages of these distalizing devices include bulky material in the palate area, and fast relapse of the molars to their forward position after device removal. The major advantage of fixed distalizing devices is that patient compliance is ensured since the device is fixed to the teeth.
Another group of devices correct the excessive overjet by holding the lower jaw forward and moving the upper teeth rearward, shifting the teeth in both jaws to a corrected position. These devices, commonly referred to as “functional appliances”, apply posteriorly-directed pressure to the upper teeth, and anteriorly-directed or protraction pressure to the lower jaw and teeth. Examples of such devices include Herbsts, twin blocks, activators, bionators, Frankels, and class II elastics. An advantage of functional appliances is that the natural pressure of the dental bite and jaws is redirected to move the teeth. Because the patient continuously bites, chews, and clenches throughout the day, constant gentle pressure is applied to the teeth. One major disadvantage of these appliances is that they are usually removable, resulting in poor patient compliance. A second disadvantage is that they are generally bulky, interfering with eating, speech, and comfort. Thirdly, these appliances generally have a fixed connection between the upper and lower jaws, which can limit jaw movement, and is bulky and unsightly.
U.S. Pat. No. 3,416,228 to Grimmett discloses a device fixed to the lower molars, which has a labial wire bow contacting the lower anterior teeth, giving attachment to a second bow which fits around the front surfaces of the upper anterior teeth. Because it cannot be removed by the patient, the '228 device solves the problem of poor patient compliance. It corrects the class II malocclusion by protracting the mandible when the patient bites together, and applies posteriorly-directed pressure to the maxilla. The chief disadvantages of the '228 device include its inability to be used simultaneously with orthodontic braces, and its poor cosmetics.
U.S. Pat. No. 4,382,783 to Rosenberg discloses a device comprising two hinges with telescoping members to join an upper and lower molar on both sides of the mouth, correcting a class II malocclusion by protracting the lower jaw. The '783 device has the disadvantages of permanently connecting the jaws which limits motion, and having parts projecting outward toward the cheeks of the patient, which can cause soft-tissue discomfort.
U.S. Pat. No. 5,848,891 to Eckhart et al discloses a device having a first member attached to the upper molar and a second member attached to the lower molar, both members projecting outward toward the cheek. The members of the '891 device are designed to prevent complete closure of the jaws in the uncorrected or retruded jaw position. Biting in this position can put extreme vertical pressure on the members, transmitting a torsion force to the molar bands, thereby resulting in frequent breakage of the bands. For this reason, a stainless steel veneer crown is frequently used to give attachment to each member. Attached to the upper and lower first molar teeth, the crowns are stronger than orthodontic bands, but are difficult to remove after treatment is completed. Another disadvantage of the '891 device is that it requires fabrication by a dental laboratory, and requires two separate appointments: a first to take a dental impression, and a second for delivery after laboratory fabrication.
U.S. Pat. No. 6,099,304 to D. Carter discloses a device having an adjustment assembly on the upper molar, and a placement assembly on the lower molar, both assemblies projecting outward toward the cheek. The '304 device, as with the '891 device, prevents complete closure of the jaws in the uncorrected bite position, causing protraction of the lower jaw to allow complete closure into the corrected bite position.
Some of these prior-art devices, such as U.S. Pat. Nos. 3,416,228 and 5,443,384 have permanent parts near the surface of the teeth which can trap food and Interfere with good oral hygiene. In addition, the device of U.S. Pat. No. 4,382,783 permanently connects the jaws which can limit jaw movement.
Other devices, such as those of U.S. Pat. Nos. 5,848,891 and 6,099,304 have parts projecting laterally towards the cheek of the patient's mouth, which can cause painful biting of the cheeks. Furthermore, both of these devices employ two members for each side of the mouth, so that each patient generally requires four members. This degree of complication generally requires construction by a dental laboratory, which requires two patient visits for device delivery to the patient. An additional disadvantage of these two devices is that, in the retruded jaw position, the patient's strong vertical biting forces can cause breakage of the tooth band, since the vertical force applied to the member is far away from the tooth, located more laterally near the patient's cheek. This transmits a torsion force to the band causing breakage and loosening. To prevent breakage, these members are usually attached to stainless steel crowns over the molar teeth, which have the distinct disadvantage of being difficult to remove.
Therefore, it would be highly advantageous to have a device and method of treating excessive overjets, which the patient cannot remove, and which take advantage of the natural bite pressure to distalize the upper teeth. It would also be beneficial to have such a device and method which do not permanently connect the jaws, allowing greater comfort and jaw movement, and still providing a non-removable device to ensure patient compliance. Additionally, it would be advantageous for this invention to allow the teeth in both jaws to be moved orthodontically with braces.
It would also be helpful for the device to be simple in design, having only one member for each side of the patient's mouth, allowing it to be prefabricated. This simple design could be prefabricated in a variety of sizes, and would require one patient appointment, rather than two, for delivery of the device to the patient. In addition, it would be beneficial for the point of biting force on the device to be located near the tooth surface, rather than laterally near the cheek, to prevent breakage and allow for the use of an orthodontic band as a means of tooth attachment. Furthermore, it would be desirable for the invention to be less visible, to enhance cosmetic appeal, and to be less bulky than traditional devices, enhancing patient comfort. Finally, it would be helpful for the device and method to avoid parts positioned near the patient's cheek, which can result in painful biting of the cheek and can interfere with proper tooth brushing.